Dear Mark: Fiber, Fat and Fasting

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Dear Mark,

I have two questions. My first regards training and rest days. Simply, how many days of complete rest should I take for an entire week? I someone who’s been overweight for most of his pre-teen and teenage life, and who was able to lose that excess weight at 17 (I’m 20 now). My current goal is to “look fit” (and be healthy), which primarily entails eliminating the stubborn fat on my body that have refused to go away. If I’m doing three days of high-intensity interval training, for around 15-20 minutes per day, and three days of 1 hour lifting, for a total of 6 days per week with one day of rest, is that doing too much?

Secondly, where do I get most of my fiber on a primal blueprint diet if most high-fiber vegetables can only be attained sparingly (I’m a poor college student)? I’ve been looking around your site for the answer, and the only thing I’ve read mentioned in passing was flaxseed. If that is your suggestion, where can I buy it? I couldn’t find it in the cereal aisle of my local grocer.

First off, because you are still trying to lose the “stubborn” fat, I just need to remind you (and other readers) that 80% of your body composition results will come from PB-style eating. Yes, you still have to exercise to build or maintain muscle and to stimulate some added fat-burning enzymes, but you don’t want to fall into the common habit of thinking you must exercise nearly every day to burn off stored fat.

OK, having said all that, the amount of rest you need depends on your work load and perhaps your level of fitness if you’re transitioning to a new exercise routine. Given the program described, I’d say your one “day off” could be completely adequate. However, I wouldn’t hesitate to add another day off if you feel like you’re not recovering between workouts. Listen to the signals your body is sending, and know the message might be different from week to week depending on sleep and stress levels, etc. If you choose to take that extra day, you can always use it to incorporate some low to moderate level “life” activity: hike, bike ride, kayaking, a game of ultimate Frisbee, or even some energy-intense house projects. Your training won’t take a hit if you take an extra day or two off. And if you’re eating well, your fat-burning won’t suffer at all.

Farmers' Market

As for the fiber question, I’ve often said that dietary fiber is over-hyped by the media. Truth be told, we don’t really need that much beyond what we get from eating vegetables and a few fruits each day. (People get themselves into trouble when they eat processed foods and throw off their body’s systems.) A natural, whole foods diet just doesn’t require “whole grains,” despite all the hoopla. Grok and his entourage did just fine without Metamucil and multigrain cereal for breakfast. Our bodies adjust to a more natural fiber intake over time. Adequate water and plenty of exercise can also help keep the pipes running. Nonetheless, here’s a list of fiber content estimates that can help you target your produce purchases. In short, apples, pears, berries, eggplants, artichokes, and all manner of raw and cooked greens are all good higher fiber options. You’ll note from this list that dried figs, yams, and a number of cooked legumes rate among the highest in fiber (10-19 grams per serving—with varied serving size) for non-grains, but (as you know) I don’t recommend these foods as regular MDA fare because of their high carb content.

Hi Mark,

Can you give me an idea on what oils to include in my diet. They are so expensive over here in the UK. I have recently bought brazil nut oil, walnut oil, and olive oil. I want to make sure I fulfill my daily needs without overlap (due to expense). Also how much of each should I be consuming. My other question is should I work out in a fasted or non fasted state.

Oils and Fat

I’m all for incorporating nuts into the diet, and nut oils offer a healthy (and tasty) alternative to canola, corn and sunflower oil. Your choices above are fine. Nonetheless, I don’t have a specific daily requirement for any particular oil. Use what you need to for flavoring and getting enough fat in your diet. To cut the expense, I’d suggest eating more whole nuts and nut butters (homemade is cheaper and pretty darn easy). Also, tropical oils, butter and lard offer cheaper options that can also be used in cooking. Each, of course, has its own distinct flavor. Experiment with them and find the best uses/recipes for each. As long as you’re going low carb, the extra saturated fat isn’t a concern. Of course, I always suggest “cleaner” versions of any animal product (especially anything high in fat, where most toxins are found).

As for working out while fasting, I don’t see a problem with it in general. Of course it depends on how long you’ve fasted, too. If you ate last night and work out this morning without eating, there’s not only no problem there, there may be a benefit in terms of fat burning if today’s workout is a long slow one, or in term of growth hormone if today’s is a short, intense workout. As for working out during a longer planned fast, if you’ve done it before and felt fine, I wouldn’t recommend necessarily dropping your workout during fasting days. You might want to dial back the intense training on extended fasts, though. Or if you’re new to fasting you might want to keep your exercise on those days low to moderate and save the heavy stuff for the rest of the week.

Ironically, whereas I would often recommend not eating immediately after a workout, if you have NOT fasted prior (in order to maximize growth hormone), it might be beneficial in this case to “break” your fast following hard resistance training sessions. In the 30 minutes to an hour following a weight workout, your body has a uniquely efficient potential for protein uptake. I’d suggest taking advantage of that timing. This goes double if you’re older or are working hard for muscle mass gain. I’m basically saying don’t regularly starve yourself for a long period both before AND after a hard workout. You can eat before and starve after or starve (fast) before and eat after. Hope that all makes sense.

Thanks, as always, for your messages. Keep ‘em coming!

buck82, jfravel, Tim Morgan Flickr Photos (CC)

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TAGS:  dear mark

About the Author

Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending three decades researching and educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates Primal/paleo, keto, and Whole30-friendly kitchen staples.

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25 thoughts on “Dear Mark: Fiber, Fat and Fasting”

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  1. Watch out when you buy lard at the store; it’s often hydrogenated! It’s cheap and better quality if you render it yourself. I posted a recipe on my blog for this a while back. I was able to get pasture-raised lard at my farmer’s market for $2/lb, making it cheaper than any other quality fat.

  2. Hey Mark,

    Totally agree on the fiber point – I eat moderate amounts of vegetables, fresh fruit and salad and none of the grain-type food normally touted as necessary for roughage: and you could set a clock by my bowels!

    Pay Now Live Later

  3. There seems to be an all out push by the cereal companies via commercials out there right now to really amp up the recognition of their fiber content in the cereal. I would like to get on the other side of this, as I am curious what public consensus out there is about fiber? It seems that these marketing people for these commercials are really trying to push this hard.
    thanks Mark.

  4. On the oil topic, I’ve often wondered if there is any sort of health difference between regular olive oil and extra virgin. Is extra virgin better?

  5. Intermittent fasting is misunderstood (and feared) enough by the general public. Let’s not equate it with “starving” here, please.

  6. Barry, extra virgin has a few more natural antioxidants, so it lasts longer on the shelf. People say it tastes better, too. It is much more expensive, so if costs is an issue, you wouldn’t be doing yourself a disservice to get the regular olive oil.

    Evan, point taken. You are correct in that we don’t want to give the wrong impression of IF. I sometimes use the term “starve” informally, since I have no emotional spin on it.

  7. For the poor college student: I highly recommend a big bag of frozen broccoli (or other frozen vegetables) Grok didn’t have freezers, but Grok also didn’t have as much of an issue managing time–papers, problem sets, projects, and extracurriculars. Frozen veggies is better than no veggies at all, can store a long time, and are convenient.

    In my opinion the primary benefits of fiber is just that it helps you eat less by making you feel fuller longer. Focus on eating plenty of vegetables and avoiding processed foods and you don’t have to worry about fiber content or supplements. The fiber recommendations are mostly targetted to the people consuming tons of white flour and sugar.

  8. I have been reading about flax oil a possible cause of prostate cancer, any opinions?

  9. i have never seen any convincing evidence for any benefits to fibre, if it comes from fruit and veg, i don’t see any benefits or problems either way. i would not even consider it as an essential dietary component -but more of a neutral option.

    What is known, however, is that GRAIN FIBRE is full of anti nutrients (the PC way of labeling toxins). all grain fibre contains to a greater or lesser extent phytic acid – which leaches vital minerals from your body, and lectins, which attack the gut mucosa lining and makes people vulnerable to auto immune responses.

    if i eat bread, i eat only unbleached traditional white bread from sour dough, the only method that eradicates these toxins.

    grains came late to the human diet. in order to make them edible, they had to be processed (fermented and crushed and cooked). Also, settled living allowed this cheap, highly productive food to be used as a staple. but it was only highly productive in the sense of quantity, not quality. it could never replace an animal, which has a complete and perfect balance of nutrients. we were never adapted to the high levels of carbs they contain, nor the antinutrients.


  10. Konstantin, I have read your book and found it very informative. I have recommended it to many people and do so here again to all reading this post. Glad you visited us here at MDA.

  11. Ken –

    Great question. We will be covering it in a future blog post. Thanks for the suggestion.

  12. Mark,

    Thank you for reading Fiber Menace, and for recommending it to your readers. Please ‘take a bite’ at its companion web site. I released the entire content of my next book — Gut Sense. It takes off on those subjects that Fiber Menace just glanced over… Hope you’ll enjoy it too!

    Thank you again,


    P.S. I am using Google Alerts to monitor anything related to fiber — it brought me to your great blog.

    1. We agree fiber isn’t that big a deal. Sometimes Grok ate a ton of vegetable fiber and sometimes he had very little.

      1. Then why do you say “I am a huge fan of fiber – in addition to consuming 7-9 daily servings of produce, I take a psyllium fiber supplement and I think everyone should.” I mean why bother if fiber is not a big deal with all this?

        1. I forget when I may have said that. I don’t do supplemental fiber anymore. Of any kind. This blog is almost three years old. Remind when and where I said that? I’ll fix it.